<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var arr =[100,26,18,89,90];//2,4,10,18
        arr.sort(function(a,b){
            return a-b
        })
var n=0
var arr1 = []
for(var i=0;i< arr.length; i++){
    if(arr[i]<60) {
        arr1.push(arr[i])
    }
// document.write("不及格人数:"+ arr1.length)
var arr3 =["唱歌","跳舞","弹琴","脱口秀","唱歌","跳舞"]
var arr4 =[]
for(var i=0;i< arr3.length; i++){
    if(arr4.index0f(arr3[i])== -1){
        arr4.push(arr3[i])
    }
}
document.write(arr4)
    </script>
</body>
</html>